Some have clips with a T bolt thru them, that unscrews under the dash to release,mainly in the corner areas.....
If the trim is inserted into the windshield rubber gasket,as on a 40's Ford,you may have to cut the gasket off with the trim. After a lot of years the trim siezes to the rubber and the trim will bend rather than releasing from the gasket. Maybe some penetrating oil would work into the trim slot to help work the trim out. Easy does it as the trim will bend very easily.